Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h, w = map(int, input().split())
field = [input() for _ in range(h)]
d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
white = 0
for i in range(h):
    white += field[i].count(".")
cnt = [[-1]*w for _ in range(h)]
cnt[0][0] = 0
q = deque([[0, 0]])

while q:
    y, x = q.pop()
    for dy, dx in d:
        ny = y + dy
        nx = x + dx
        if 0 <= ny < h and 0 <= nx < w and field[ny][nx] == "." and cnt[ny][nx] < 0:
            cnt[ny][nx] = cnt[y][x] + 1
            q.appendleft([ny, nx])
        if ny == h-1 and nx == w-1:
            print(white - cnt[h-1][w-1] - 1)
            exit()

print(-1)